Physics and Mathematics
Two Kinds of Charges
1. Statement of the Concept
There are two types of electric charges found in nature:
- Positive charge
- Negative charge
Objects interact electrically based on the nature of charge:
- Like charges repel
- Unlike charges attract
This fundamental fact was first established by Benjamin Franklin.
2. Clear Explanation
What Are the Two Kinds of Charges?
Matter consists of charged particles:
- Proton → +e
- Electron → −e
So the two types of charge arise naturally from the properties of protons and electrons.
How Do Charges Interact?
Experiments show:
- Two positive charges repel each other
- Two negative charges repel each other
- A positive and a negative charge attract each other
This is the basis of all electrostatic interactions.
Origin of Charging of Bodies
Bodies become charged when electrons move:
- If electrons are gained, body becomes negatively charged.
- If electrons are lost, body becomes positively charged.
No Third Type of Charge
All known particles carry either:
- Positive charge
- Negative charge
- Or are neutral (equal + and − charges)
There is no third type.
3. Dimensions and Units
Charge (for both types):
| Quantity | Unit | Symbol | Dimension |
|---|---|---|---|
| Electric Charge | Coulomb | C | [IT] |
4. Key Features
- Two types of charges: positive and negative
- Magnitude of charge is always in multiples of [e]
- Like charges repel; unlike attract
- Positive charge corresponds to a deficit of electrons
- Negative charge corresponds to an excess of electrons
- Charge interaction is a non-contact force
- All charge interactions follow Coulomb’s Law
5. Important Formulas to Remember
| Concept | Formula |
|---|---|
| Positive/Negative charge | [ q = \pm ne ] |
| Elementary charge | [ e = 1.6 \times 10^{-19} \text{ C} ] |
| Total charge | [ Q = \sum q_i ] |
| Net charge after electron transfer | [ q = \Delta n , e ] |
6. Conceptual Questions with Solutions
1. Why are there exactly two kinds of charges?
Because matter contains two charged particles: protons (+e) and electrons (−e). All observed charges originate from them, giving only + and − types.
2. Why do like charges repel and unlike charges attract?
It is an experimentally established fundamental law of nature. Coulomb’s law supports it mathematically, showing force direction reverses with sign of charge.
3. If protons are positive, why does a body become positively charged when electrons are removed?
Because the number of protons becomes greater than electrons. Protons are not added; electrons are removed.
4. Is it possible to create new types of charge?
No. Charge is a fundamental property of particles. Only +e, −e, or 0 have ever been observed.
5. Why does a negatively charged body have excess electrons but not increased protons?
Because only electrons move between bodies. Protons are tightly bound in the nucleus.
6. Can a body have both positive and negative charge simultaneously?
On a microscopic scale, yes—parts may have both types—but overall the body will have a **net** charge based on excess or deficit of electrons.
7. Why do neutral objects have no net charge?
Because they have an equal number of positive and negative charges, giving [q = 0].
8. Can two negatively charged bodies attract each other?
No. Like charges always repel under electrostatic interaction.
9. Why is charge on an electron negative and not positive?
It is convention. Franklin arbitrarily called one type positive, and electron’s charge fell into the negative category.
10. If an object becomes negative, does its mass increase?
Yes, slightly. Adding electrons increases mass by a tiny amount.
7. FAQ / Common Misconceptions
1. “Positive charge means protons are added.”
No. Positive charge means electrons are removed. Protons do not move.
2. “Negative charge means protons are removed.”
No. Negative charge comes from **gaining electrons**, not losing protons.
3. “Neutral objects have no charges inside.”
Incorrect. They contain equal positive and negative charges.
4. “A charged body must have only one type of charge.”
No. It contains both types, but the **net** charge is determined by electron imbalance.
5. “Like charges attract if the objects are large enough.”
No. Like charges **always repel**, regardless of size.
6. “Positive charge is stronger than negative charge.”
No. Both have equal magnitude: [+e] and [−e].
7. “Electrons can be removed from the nucleus.”
False. Electrons are removed from the outer shells, not the nucleus.
8. “All charged bodies interact equally with all other charged bodies.”
No. The force depends on distance and magnitude of charges via Coulomb’s law.
9. “Neutral bodies cannot participate in electric interactions.”
Incorrect. They can attract charged bodies through induction.
10. “Charges can exist without matter.”
No. Charge is a property of matter and cannot exist independently.
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